The data management and methodology (DM&M) core will provide two major services to all research and scientific cores. (i). A computerized database will be maintained in which will reside all longitudinal research data obtained from questionnaire, telephone and personal interview, all derived measures, and all diagnostic variables. This core will also implement rigorous methods for data entry, editing, and updating and will give highest priority to ensuring that the data is clean, consistent and secure. The DM&M core will provide a documentation for easy access to the database an will also provide the support and expertise in using the database to all MARC investigators. Major existing local and national databases will be maintained by this core (under the direction and guidance of the A&N core) providing investigators easy access to these data. (ii) The DM&M core will provide an infrastructure for consultation and data analytic support to each core and research component as well as to other local, national, and international collaborators on issues relating to data collection and methodological analyses of longitudinal family and twin data. The methodological research within the DM&M core will initially focus on complex survival analytic structural equation, and other regression models for longitudinal data analysis. Basic research will address the utility of latent class analysis, cluster analysis, and artificial neural networks for distinguishing subtype variation or classification problems. This core will take a proactive role in encouraging and stimulating researchers to test complex hypotheses and to help guide the methodological processes of MARC research. It will promote synergistic interaction among all components by promoting ongoing communication regarding data management and methodological issues. The DM&M core will also play a lead role in data- analyses to test Center-wide hypotheses, working under the direction of the Research Coordinating Committee of the Administrative Core.